X-ray tube



Nov. 9, 1937. D. G. SHARP` 2,098,315

X-RAY TUBE Filed July 14, 1934 INVENTOR 6'. SHA/ip BYI/-of ATTORN CalPatented Nov. 9, 1937 UNiThD STAEES hA'ifN'i Qtr-FISE X-RAY TUBEApplication `uly 14, 1934, Serial No. 735,181 Y temperature drop betweena surface tobe cooled occurs 'at'thepoint of contact'of the lm'with theheated surface as compared with about '75% ofthe temperature drop.occurring at thispoint `6 Claims.

My invention relatesto X-ray devices and comprises in ,particular anewX-ray anode or target which is particularly'adapted'for use inconnection with the continuousgeneration of X-rays,

for example, in the administration of therawith Water. 5 peuticaltreatments. Also consideration ofthe factors of `density and It is usualin the construction of X-rays tubes specific heat vmakes it vessentialthat at least to provide a surface of refractory metal, such as rtwiceIthe flow 'of oil is necessary to dissipate a tungsten or the like,molecularly secured to a given amount of heat as Would be required instem of good heat conducting metal, such as water cooling assumingidentical ticonditions of l0 copper. During operation of the tube theelectransfer which, as Vabove noted, do not exist. tron stream is moreor less concentrated upon Moreover, this necessity'for increased owwhenthe refractory metal surface resulting in the utilizing oil lsrfmadestill more difficult by the generation of considerableheat, which istransgreater viscosity thereof 4at all temperatures, mitted to the stem.The energy for-the tube is which `diierence is very marked yin 4they'cooler 15 supplied from a high'tension source to be rectiparts of thecirculating-system, fled by the' tubeitself OIbY'IlteImttent direct kOf:all .theafo-renoted factors those of density, current when a `separaterectifier is employed. thermal conductivity and specific heat remainUnder either ofv these conditions the anode surface constantfor a givenmedium, but I have found the or targetis subject to `severemechanicalshocks .factors ofl .lming and Viscosity canbe advan- .20caused .by the intermittent bombardment thereof tageously dealt with..By increasing' theY turbuaccompanied by periods 0f intense heating fol-`lence of cw the thickness of-the nlm at the lowed by like intervalscfcooling. This has a tensurfaces of greatest heat may be reduced, whichdenCY vt0 Cause 'Cracking and tearing of the reit should be noted, isaugmented by thefact that 'fractory metal surface as Well as a bucklingaway the viscosity ofthe oil is'lowest because of the v25 from the backplate. high rtemperature at` this point thus reducingthe For the purposeof preventing undue heating resistance tofow. of the anode in X-raytubes when employed for Furthermore, by increasing'the Velocity Yof flowtherapeutical treatments or other conditions re- .of the medium notonlyis the thickness 'ofthe quiring a heavy load, it is common to circulatea film reduced, but the tendency of hydrocarbon 30 cooling andinsulating material through the anoils t0 carhonize `at the points ofhigh temode narl endeavor to maintain an even teIIl- Yperature is alsosubstantiallyeliminated, due to Delatllle- If Water 1S employed thedeVCe CaImOt the fact that the oil is in vContact with the highly beadVantageOuSly rendered Shockproof because heatedsurface but a verybriefinstant owing to of thehigh voltages to which the tube is subjected thehigh turbulence and Velocity thereof. '.35 and the fact that Water isnot dependable as a kIt is. accordingly an object of my presentindelectlc medium- AS a COIlSeGlllEIICe a high dvention to provide an.X-ray tube suitable for electric uid is normally utilized, such ashydrocontinuous Operation wherein an ,anode is procarbon oils, but evensuch uid requires special vided through which a cooling and insulatingtreatment t0 DIOPBTIY adapt them OI anode C001- material, suchas oilcirculates, at high velocity `:i0 ing pUIDOSeS. thereby increasing theeiiciency of :heat trans- In the utilization of any cooling mediumA oneof :fer from the heated surfaces to themedium. the mOSt importantfaCtOlS iS tluloulerlli or hy- Another object of my invention is theprovision draulic iiow, which is absolutely necessary to of an X-raytubehaving an anode which beecelt heat eXChalge in that there iS alwayscomes heated during operation of the tube and v45 a film of the mediumin contact with the walls wherein a cooling and insulatingY medium of ofthe passage through which it flows. The heat khigher viscosity thanwater is caused to circulate from the body to be cooled must betransmitted therethrough at a high velocity thus reducing through thislmto the turbulent body of a well :thetendency of the mediumto film.mixed cooling fluid. When cooling and insulat- A further object of mypresent invention is the .50 ing materials, such as hydrocarbon oils andthe provision of an X-.ray tube `having an anode like, are employed forcooling purposes there is a which becomes heated during operation of thegreater tendency for the same to film overthe tube and wherein a coolingand insulating Vmasurface due to its high viscosity and,'because ofterialof ycomparatively high viscosity circulates its 10W thermalconductivity. about 99% oi the Atheretlm)ugh at high velocity andturbulence thusre increasing the eiiiciency of heat transfer andsubstantially eliminating the probability of carbonizing of the mediumat pointsrof greatest heat.

Still further objects of my present invention Will become obvious tothose skilled in the art by reference to the accompanying drawingwherein:

Figure 1 is a side view of an X-ray tube constructed in accordance withmy present invention,

Fig. 2 is a longitudinal sectional view of the anode construction of mytube,

Fig. -3 is a sectional View taken on the line III-III of Fig. 2 lookingin the direction of the arrows, and Y Fig. 4 is a sectional view takenYon fthe line IV-IV of Fig. 2 looking in the direction indicated by thearrows. a

Referring now to the drawing shown in Fig. 1 an X-ray tube comprising anevacuated envelope 5 having a reentrant sleeve Y6 forming an inner foldextending a substantial distance longitudinally of the envelope to wellof this reentrant sleeve l.

A further reentrant stern I2 extendsinwardly of the envelope and hassealed thereto the anode electrode I3 which receives energy through acon- Y ductor I4. By reference more particularly to Fig. 2 this anodecomprises a hollow metallic member I5, such as spun copper or the like,sealed to this reentrant portion of the envelope.V

A head or back plate I6 of good heat conducting material, such as copperor the like, is molecularly secured to the member I5 and this head inturn is provided with a target face I'I of a refractory metal, such astungsten, secured thereto adjacent the cathode which Vreceives theelectron bombardment during operation of the tube.

This electron bombardment being more orV less concentrated upon thetarget I'l, causes the generation `of considerable heat particularlywhen the tube is continuously operated for long periods of time as inthe administration of therapeutic treatments. This heat is in turntransmitted to the copper head or back plate I6 and in order to transferthis heat and maintain the temperature of the entire anodesubstantiallyv uniform I provide a structure for circulating aninsulating Yand cooling medium through the anode stem.

The interior of the hollow member or anode stemV I5 has suitably securedthereto an annular threaded ring or the like I8 and an elongated thimblelike member I9 is arranged to threadedly engage this ring I8 beingscrewed in place by a suitable tool engaging recessesv 20 provided inthe thimble. rlhe thimble I9 is provided with a shoulder portion 22 ofincreased diameter'with its outer periphery spaced closely to theinterior of the member I5 and the endV of this thimble I9 is providedwith a concave surface or face 23 spaced a Short Ydistance from the endof the member I5 to which the copper head I 6 is secured. While Ihave-shown the member I5 as having a closed end to provide more surfacearea for the purpose of molecularly Vsecuring the back in detail I haveplate I t thereto and to facilitate ease of construction, it is to beunderstood that this may be open ended thus allowing the face 23 to bespaced a short distance directly in the rear of the back plate I5.

Moreover, this end of the member I5 is more or less integrally unitedwith the back plate IB and for all intents and purposes may beconsidered as a part thereof. Accordingly throughout my specication andclaims I shall refer to the back plate as being spaced directly from theface 23 of the thimble I9 and directly contacted by the cooling andinsulating material. 'I'he opposite end of the thimble is likewiseprovided with a shoulder portion 24 and a series Vof spacer Washers 25are disposed between this shoulder portion 24 and the annular ring I8for the purpose of adjusting the spacing between the concave end surfaceof the thimble and the adjacent surface of the back plate I6.

A longitudinal opening having a reduced diameter portion 26 and aportion'ZI of larger diameterv Yextends through the thimble I 9 from thecenter of the concave face 23. An inlet conduit 28 of suitableinsulating material, such as hard rubber or a phenolic condensationproduct, threadedly engages tiie reduced diameter portion 2E andprojects' beyond the envelope for connection to a suitable oilreservoir. Y

In a similar manner a concentrically disposed outlet conduit 29surrounds the inlet conduit which is formed of the same insulatingmaterial and threadedly engages the thimble I9 at its increased diameterportion 2'I. A plurality of radi- 'ally disposed passagesY V30, as shownmore clearly vtion of Louis F. Ehrke, Serial No. 754,231 filed November22, 1934 and assigned to the same assignee as the present invention, andalso to the thimble I5 to prevent clinging of the cooling and insulatingmaterial with the formation of an undesirable deposit as hereinaftermore fully described. v

In the operation of the tube a cooling and insulating material, such asa high grade hydrocarbon oil, is caused to flow from a suitablereservoir through the inlet conduit 28 toV the concave face 23 of thethimble I9. Due to the spacing between this end of the thimble and therear surface of the back plate I6, which is the point of greatest heat,as well as the configuration of the thimble surface 23 a high turbulenceof the oil results with an attendant high velocity in the flow thereof.This accordingly prevents too great a illming of the oil at the point orsurface of greatest heat with a rapid flow of sufficient volume 0fV thefluid to transfer the generated heat thereto. The oil then circulatesaround the periphery of the shoulder portion 22 into the annular passageformed by the latter and the ring I3 after which it enters the outletconduit 29 throughV the radial openings 3) and returns to the reservoirfor cooling.

Y prevents, too great a filming of the oil witha concentration of heattransfer at the surface of greatest heat, but likewise eliminates thepcssi- Y 'bility of the oil carbonizing by leaving deposits which wouldordinarily occur offering an impediment to the flow thereof, as well asacting as a heat insulator. This is further augmented by the coating ofnickel or other metal upon the greater portion of the surface of thecopper thimble I9 and the adjacent surface of the member l5, which iscontacted by the oil when at its highest temperature. The possibility ofthe cil forming a chemical deposit with the copper is eliminated by thismetallic coating which has a polished surface offering less resistanceto the flow of the heated oil as well as the fact that the particularmetal employed has a less anity for the various elements composing theoil than would copper. This latter feature of providing the coating 32upon the inner surface of the hollow anode stem l5, however, forms nopart per se of my present invention but is specifically shown andclaimed in the aforenoted copending application.

It thus becomes obvious to those skilled in the art that I have providedan X-ray tube suitable for `continuous operation for therapeuticalpurposes wherein an anode is provided through which a cooling andinsulating material circulates for transferring the heat generatedduring operation of the tube. By increasing the turbulence andmaintaining a constant velocity of iiow at the surface of greatest heatan increase in the efficiency of heat transfer is obtained. Moreover, byincreasing the velocity of flow at the critical area or region wherehigh turbulence is needed and low viscosity is available through hightemperature, resistance to the flow of oil in this region is reduced toa minimum, and the maximum amount of oil surface is presented in thepath of heat flow immediately in back of the target without possibilityof resulting carbonization of the oil.

Although I have shown and described one specific embodiment of myinvention I do not desire to be limited thereto as various othermodifications thereof may be made without departing from the spirit andscope of the appended claims.

What is claimed:

l. An X-ray tube comprising an envelope, a cathode, an anode including arefractory metal target which becomes heated during operation byelectron bombardment, a back plate of good heatI conducting material forsupporting said target and a hollow anode stem for supporting said backplate, and means for uniformly circulating a cooling and insulatingmaterial over the maximum surface area of said back plate rearwardly ofsaid target including a member disposed interiorly of said anode stemhaving passages for the ingress and egress of a cooling and insulatingmaterial, and said member being of such size relative to said back plateand having a concave surface spaced a short distance from the adjacentrear surface of said back plate so as to impart a, high turbulence andhigh velocity to said cooling and insulating material at all points ofgreatest heat to enable said material to flow over the surface of saidback plate without lming and to effect maximum heat transfer from saidanode to said cooling and insulating material.

2. An X-ray tube comprising an envelope, a cathode, an anode including arefractory metal target which becomes heated during operation byelectron bombardment, a back plate of good heat conducting material forsupporting said target and a hollow anode stem for supporting said backplate; and means for uniformly circulating a cooling and insulating'material over the maximum surface area of said back plate rearwardly ofsaid target including a member threadedly engaging the interior of saidanode stem provided with a concave surface spaced from the adjacent rearsurface of said back plate and having a smooth polished coating of ametal offering a negligible resistance to the flow of a cooling andinsulating material, and inlet and outlet passages provided in saidmember for the circulation cf a cooling and insulating materialinteriorly of said anode stem and in Contact with said back plate, saidinlet passage terminating coaxially with the concave surface of saidmember whereby a high turbulence and high velocity is imparted by saidconcave surface to said cooling and insulating material at points ofgreatest heat to cause flow thereof over the maximum surface area ofsaid back plate with substantially no resistance thereto and maximumheat exchange is effected between said anode and said cooling andinsulating material.

3. An X-ray tube comprising an envelope, a cathode, an anode including arefractory metal target which becomes heated during operation byelectron bombardment, and means disposed interiorly of said anode forcirculating a cooling and insulating material at a high constantvelocity interiorly of said anode, said means being spaced in closeproximity to the rear surface of said anode immediately in back of saidtarget and having a surface of a diameter slightly less than theinternal diameter of said anode, and said surface being angularlydisposed relative to the rear surface of said anode so as to impart ahigh turbulence to said material to cause a rapid flow thereof over themaximum surface of greatest concentration and to effect efcient heattransfer from said anode to said material without the formation of aheat-absorbing film impeding the uniform flow of said material.

4. An X-ray tube comprising an envelope, a cathode, an anode including arefractory metal target which becomes heated during operation byelectron bombardment and a back plate of good heat conducting materialfor supporting said target, and means disposed interiorly of said anodefor circulating a cooling and insulating material Vat a high constantvelocity immediately in back of said back plate, said means being spacedin close proximity to the surface of said back plate and having asurface of a diameter slightly less than the internal diameter of saidanode, and said surface being angularly disposed relative to the surfaceof said back plate so as to impart a high turbulence to said material tocause a rapid flow thereof over the maximum surface of greatest heatconcentration of said back plate and to effect efficient heat transferfrom said anode to said material without the formation of aheatabsorbing film impeding the uniform flow of said material.

5. An X-ray tube comprising an envelope, a cathode, an anode including arefractory metal target which becomes heated during operation byelectron bombardment and a back plate of good heat conducting materialfor supporting said target, and means for uniformly circulating acooling and insulating medium over the maximum surface area of said backplate including a member spaced from said back plate having passages forthe ingress and the egress of a cooling and insulating material, andsaid member having a surface adjacent to said back plate spaced in closeproximity thereto and of a diameter slightly less than the internaldiameter of said anode in order to impart a high turbulence and a highvelocity to said cooling and insulating material immediately in back ofsaid back plate to enable the material to ow uniformly over the entiresurface of said back plate of greatest heat concentration and to eectmaximum heat transfer from said anode to said Vcooling and insulatingmaterial.

6. An X-ray tube comprising an envelope, a cathode, an anode including arefractory metal target which becomes heated during operation byelectron bombardment and a back plate of good heat conducting materialfor supporting said target, and means for uniformly circulating acooling and insulating material of comparatively high viscosity over themaximum surface area of said back plate rearwardly of said targetincluding a member spaced from said back plate have ing passages for theingress and the egress of a cooling and insulating material, said memberhaving a surface adjacent to said back .plate in close proximity theretoand of a diameter slightly less than the internal diameter of said anodein'order to impart a high turbulence and a high velocity to said coolingand insulating material immediately in back of said back plate and tocause the material to iiow uniformly over the entire surface of saidback plate Without forming an impediment to the iiow thereof, torpresentmaximum amount of cooling and insulating ma'- terial surface in the pathof greatest heat flow Vto effect maximum heat exchange between saidanode and said cooling and insulating material.

D. GORDON SHARP.

